1. Field of the Invention
The present invention relates to golf shoes, and more particularly to an improvement in a pattern of a bottom surface of golf shoes.
2. Description of the Related Art
When hitting a golf ball, a golf player sets an address such that a line connecting right and left tiptoes are in almost parallel with a hitting direction. In an address for a right-handed golf player, a left foot is positioned on the front side in the hitting direction and a right foot is positioned on the rear side in the hitting direction. In the address, a head of a golf club is positioned close to a golf ball. In this state, the golf player starts take-back, pulls the head rearward and then swings the golf club upward. The highest position of the head swung upward is equivalent to a top position. In the top position, a downswing is started and the head is swung downward so that the head impacts the golf ball. After the impact, the golf player swings the golf club forward and then upward (follow-through). Thus, a finish is attained.
From the top position to the finish, the golf player carries out a body turn by setting a left foot as a pivot. At the same time, the golf player kicks the ground by a right foot to transmit the force to the golf ball. In other words, a right-handed golf player uses a left foot as a pivoting foot and a right foot as a kicking foot. To the contrary, a left-handed golf player uses a right foot as a pivoting foot and a left foot as a kicking foot.
From the top position to the finish, great force is applied to both feet of the golf player. In some cases, the force causes golf shoes to slip off from the ground. In some cases in which the slip is caused, a swing form is disordered so that a misshot is generated.
In order to attain slip prevention, a needle-like spike pin formed of metal or ceramics is provided on the bottom surfaces of the golf shoes in some cases. In such golf shoes, the slip is considerably prevented. However, there is a problem in that the spike pin damages a lawn in a putting green, a floor in a clubhouse and a road surface of a passage for walking which is provided in a golf course. Moreover, the golf shoes having the spike pin give a push-up feeling and are not comfortable for the golf player to wear. In recent years, the golf shoes having the spike pin have not been preferred for use.
Golf shoes having a projection formed of rubber or synthetic resin which are provided on bottom surfaces in place of the spike pin have been proposed and spread. Such golf shoes rarely damage a lawn and are very comfortable to wear. In the golf shoes, however, there is a problem in that the projection has less slip prevention performance than the spike pin. Japanese Patent No. 2946215 has proposed golf shoes in which a shoe for a left foot and a shoe for a right foot have different projection patterns in consideration of a difference in a role between the left and right feet. In respect of an enhancement in the slip prevention performance, however, the golf shoes still leave room for an improvement.
The present inventor investigated a vector of force applied to feet from the top position to the impact (that is, a magnitude and a direction) and found the following.
For a pivoting foot, force is roughly applied in a direction from a heel to a toe (which will be hereinafter referred to as xe2x80x9ca front directionxe2x80x9d. In detail, the force is mainly applied to a rear portion in the hitting direction of the foot in the top position (toward an inside for the pivoting foot of the golf player) and the direction is also equivalent to a slightly rearward front direction. Depending on the progress of a swing, the position to which the force is mainly applied is transferred to the center of the foot, and then a front portion (toward an outside for the pivoting foot of the golf player). Depending on the progress of the swing, moreover, the direction of the force is also transferred in a completely front direction, and then in a slightly forward front direction. It is supposed that these changes are caused by a body turn using a pivoting foot as a pivot and movement of a weight.
For a kicking foot, force is roughly applied in a direction from a toe to a heel (which will be herein after referred to as xe2x80x9ca back directionxe2x80x9d. In detail, the force is mainly applied to a front portion in the hitting direction of the foot in the top position (toward an inside for the kicking foot of the golf player) and the direction is also equivalent to a slightly forward back direction. Depending on the progress of a swing, the position to which the force is mainly applied is transferred to the center of the foot, and then a rear portion (toward an outside for the kicking foot of the golf player). Depending on the progress of the swing, moreover, the direction of the force is also transferred in a completely back direction, and then in a slightly rearward back direction. It is supposed that these changes are caused by movement of a weight from the kicking foot to the pivoting foot at the time of the start of a downswing and the subsequent rotation of the kicking foot.
The present invention has been made based on these knowledges and has an object to provide golf shoes which can be prevented from slipping during a golf swing.
In order to achieve the above-mentioned object, the present invention provides golf shoes comprising a shoe for a pivoting foot which is positioned on a front side in a hitting direction and a shoe for a kicking foot which is positioned on a rear side in the hitting direction when a golf player is to hit a golf ball, the shoe for a pivoting foot and the shoe for a kicking foot including a outsole body, and a large number of projections formed of rubber or synthetic resin are provided on a bottom surface of the outsole body, wherein the projections having a convex side wall in a direction of a toe are mainly formed on the shoe for a pivoting foot and the projections having a convex side wall in a direction of a heel are mainly formed on the shoe for a kicking foot.
In the golf shoes, projections corresponding to a fluctuation in a vector of force applied to each of the pivoting foot and the kicking foot during a swing are formed in the shoe for the pivoting foot and the shoe for the kicking foot, respectively. More specifically, the projection includes a side wall which is almost orthogonal to the vector of the force at each of points from a top position to an impact position. Accordingly, it is possible to prevent the golf shoes from slipping off from the ground (a slip in almost a direction of a toe of the shoe for the pivoting foot and a slip in almost a direction of a heel of the shoe for the kicking foot).
It is preferable that an interior angle formed by the convex side wall in the direction of a toe and the outsole body over a vertical section of the shoe for a pivoting foot should be 60 degrees or more. It is preferable that an interior angle formed by the convex side wall in the direction of a heel and the outsole body over a vertical section of the shoe for a kicking foot should also be 60 degrees or more. By setting the interior angle to 60 degrees or more, the slip prevention performance of the golf shoes can be more enhanced.
It is preferable that a ratio of a total grounding area of the projections to a bottom surface area of the outsole body in each of the shoe for a pivoting foot and the shoe for a kicking foot should be 20% to 80%. Consequently, the slip prevention performance of the golf shoes can be more enhanced.
It is preferable that the number of the projections in each of the shoe for a pivoting foot and the shoe for a kicking foot should be 10 to 1000. Consequently, the slip prevention performance of the golf shoes can be more enhanced.
It is preferable that the projections of the shoe for a pivoting foot should be formed along a convex line in a direction of a toe. It is preferable that projections of the shoe for a kicking foot is formed along a convex line in a direction of a heel. Consequently, the slip prevention performance of the golf shoes can be more enhanced, and the easiness for a golf player to swing can be improved.